Backpack



FIG. 1 is a perspective view of a backpack showing our new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a left side view thereof; and,

FIG. 6 is a top view thereof.

The structural features depicted by broken lines have been shown for the purpose of illustrating portions of the backpack that form no part of the claimed design. It is understood that the unshaded regions form no part of the claimed design. 

CLAIM The ornamental design for a backpack, as shown and described. 